# A Theoretical Paradigm for Thermal Rectification via Phonon Filtering and Energy Carrier Confinement

## TL;DR

This paper introduces a theoretical framework for thermal rectification in solid-state devices using phonon filtering and energy carrier confinement, enabling significant rectification ratios without relying on ballistic phonon transport.

## Contribution

It develops a modified phonon gas model to predict thermal rectification via phonon population control in graded thin films, a novel approach in thermal management.

## Key findings

- Thermal rectification ratios between 0.75 and 6 predicted for diamond thin films.
- Significant rectification achievable without ballistic phonon transport.
- Framework applicable to designing advanced solid-state thermal devices.

## Abstract

We provide a theoretical framework for the development of a solid-state thermal rectifier through a confinement in the available population of phonons on one side of an asymmetrically graded film stack. Using a modification of the phonon gas model to account for phonon filtering and population confinement, we demonstrate that for an ideal material, with low phonon anharmonicity, significant thermal rectification can be achieved even in the absence of ballistic phonon transport. This formalism is used to illustrate thermal rectification in a thin-film of diamond (1-5 nm) graded to dimensions > 1 {\mu}m exhibiting theoretical values of thermal rectification ratios between 0.75 and 6. Our theoretical formulation for thermal rectification is therefore expected to produce opportunities to design advanced solid-state devices that enable a variety of critical technologies.